1-Aminocyclopropane-1-carboxylate (ACC) deaminases fromMethylobacterium radiotoleransandMethylobacterium nodulanswith higher specificity for ACC

Abstract

The 1-aminocyclopropane-1-carboxylate (ACC) deaminases (EC 3.4.99.7), the key enzymes of degradation of the precursor of the phytohormone ethylene, have not been well studied despite their great importance for plant-bacterial interactions. Using blast, the open reading frames encoding ACC deaminases were found in the genomes of epiphytic methylotroph Methylobacterium radiotolerans JCM2831 and nodule-forming endosymbiont Methylobacterium nodulans ORS2060. These genes were named acdS and cloned; recombinant proteins were expressed and purified from Escherichia coli. The enzyme from M. nodulans displayed the highest substrate specificity among all of the characterized ACC deaminases (Km 0.80 ± 0.04 mM), whereas the enzyme from M. radiotolerans had Km 1.8 ± 0.3 mM. The kcat values were 111.8 ± 0.2 and 65.8 ± 2.8 min(-1) for the enzymes of M. nodulans and M. radiotolerans, respectively. Both enzymes are homotetramers with a molecular mass of 144 kDa, as was demonstrated by size exclusion chromatography and native PAGE. The purified enzymes displayed the maximum activity at 45-50 °C and pH 8.0. Thus, the priority data have been obtained, extending the knowledge of biochemical properties of bacterial ACC deaminases.

Biotechnological and Agronomic Potential of Endophytic Pink-Pigmented MethylotrophicMethylobacteriumspp.

“…Plant growth stimulation by endophytic bacteria is largely due to phytohormone production, and several studies have been reported the interaction of Methylobacterium species with different plant species by regulating phytohormone production [ 60 ]. Methylobacterium strains have been reported to produce phytohormones such as cytokinins and auxins [ 61 ], which promote cell division and elongation, respectively.…”

“…The acd S gene encodes an ACC deaminase enzyme that converts ACC into ammonia (NH 3 ) and α -ketobutyrate. An analysis of the genomes of Methylobacterium species revealed that the plant-associated species, such as M. oryzae , M. nodulans , and M. radiotolerans , contain this ACC deaminase gene [ 40 ] and that M. nodulans and M. radiotolerans are able to use ACC as a nitrogen source by the actions of ACC deaminase, reducing ethylene levels [ 60 ] and consequently the stress ethylene response in the host plant. Joe et al [ 68 ] reported that the association between an ACC deaminase-positive M. oryzae CBMB20 strain with Azospirillum brasilense CW903 strain reduced ethylene levels in plants.…”

“…Similar results were observed in canola: when a plant-growth promoting Methylobacterium containing ACC deaminase was inoculated into canola roots, it also reduced the concentrations of ACC and ethylene in the plant, increasing root length [ 65 , 66 ]. Therefore, bacteria that are able to reduce ethylene levels in the host plant are associated with plant growth promotion [ 39 , 60 , 66 ].…”

Prediction of Ionizing Radiation Resistance in Bacteria Using a Multiple Instance Learning Model

“…In particular, the IRRB M. radiotolerans (B11) and the IRSB B. abortus (B15) present a high rate of failed predictions. It means that in most cases, M. radiotolerans is predicted as IRSB and B. abortus is predicted as IRRB; the former is an intracellular parasite (Halling et al, 2005) and the latter is an endosymbiont of most plant species (Fedorov et al, 2013). A probable explanation for these two failed predictions is the increased rate of sequence evolution in endosymbiotic bacteria (Woolfit and Bromham, 2003).…”

The Role of Rhizobial ACC Deaminase in the Nodulation Process of Leguminous Plants

“…Bradyrhizobium japonicum is also able to degrade ACC through ACC deaminase production [71]. Recently, Fedorov et al [72] have characterized Methylobacterium nodulans ACC deaminase enzyme. ACC deaminase activity has also been demonstrated in members of -rhizobia, 4…”